1. Field of the Invention
The present invention is directed to an apparatus and method for assembling remote grip ferrule-based optical fiber connectors.
2. Background
In the area of optical telecommunication networks, fiber optic connectors are one of the primary ways to connect two or more optical fibers. There are several classes of optical fiber connectors including adhesive ferruled connectors, in which the fiber tip is held in a substantially fixed position relative to the end face of the ferrule by adhesively securing the fiber within the bore of the ferrule. A second class of connectors includes non-ferrule connectors, which rely on the buckling of a length of fiber to create contact pressure when mated to another connector or to a connector receptacle. Another class of connectors includes remote grip (ferruled) connectors, where the fiber is secured at some distance away from the terminal end or tip of the fiber.
When installing a remote grip connector in the field, one current practice uses a coplanar/flush polish which is done after the fiber is secured within an optical fiber connector. In remote grip connectors, as with other connector types, low optical losses and minimal reflections are achieved when the terminal ends of at least two optical fibers make secure physical contact. However, any differences in the coefficient of expansion between the fiber, the ferrule, etc. within the assembly may result in a non-contacting fiber tip when the temperature is raised or lowered. The resulting gap can lead to poor insertion loss and significant back reflection. Conventional remote grip connectors are described in U.S. Pat. No. 5,408,558 and U.S. Patent Publication No. 2008-0226236.
Another current practice involves a technician performing a field polish to create a fiber terminal end which protrudes slightly beyond the ferrule tip (i.e. the protrusion length of the fiber). This method of polishing remote grip connectors can produce a range of protrusion lengths that can provide a secure physical contact while avoiding excess force on the fiber tips.
Independent of whether using a flush polish, a protruding polish, or no polish, it is beneficial to secure the fiber so that the fiber tip protrudes a known amount. In the case where the fiber is polished after insertion, setting the protrusion and securing the optical fiber in the optical fiber connector, the amount of polishing needed can be minimized. In the case where no final polishing is done to the fiber, the protrusion setting step of the assembly process defines the final protrusion of the fiber from the end face of the connector ferrule. For example, a method of setting fiber protrusion is described in U.S. Pat. No. 7,194,179 and U.S. Patent Publication No. 2010/0316344.
Before inserting the fiber into a connector, the fiber is typically stripped and cleaved. Removing of any jacket material from the fiber optic cable and stripping away the buffer coating exposes the bare glass fiber which can then be fitted through a standard fiber optic connector ferrule. Cleaving provides an end face that can be nearly perpendicular to the axis of the fiber and reduces the amount of polishing required. In some applications, an angle cleave (e.g. of less than about 10°) can be used to improve the performance of the optical fiber connector. An appropriate cleave length (the distance between the fiber tip and the end of the polymer coating) is necessary to ensure that a sufficient amount of fiber can extend beyond the tip of the ferrule.
Viewing the glass fiber protruding from the end face of the ferrule prior to securing the fiber in the connector provides the assurance that the fiber has been successfully inserted through optical fiber connector.